To preserve tab order and to make it easier for screen readers to read your documents, use a logical heading order and the built-in formatting tools in Word.
Think of headings in the same way you think of document outlines:
The title of a document describes / encompasses the entire document. If the title appears at the beginning of your Word document, format it as a Heading 1.
For each subheading that occurs thereafter, format them equally as Heading 2.
If the Heading 2 subheadings require subheadings themselves, format them equally as Heading 3.
And so on…
Here’s a visual illustration:
(Note: Subordinate level headings and subheadings don’t have to be indented each time — the indentions were added in the examples above to simply illustrate the hierarchy of levels.)